Method of producing a lightweight foamed metal



United States atent 3,300,296 METHOD OF PRODUClNG A LIGHTWEIGH FOAMEDMETAL Paul Wilson Hardy and Glenn William Peisker, Barrington, Ill.,assignors to American Can Company, New

York, N.Y., a corporation of New Jersey No Drawing. Filed July 31, 1963,Ser. No. 299,071

29 Claims. (Cl. 7520) This invention relates to a method ofmanufacturing a lightweight foamed metal. More particularly, it relatesto a method whereby the fluidity of a plastic metal mass is decreasedduring foaming and the foaming is carried out by the formation of gasfrom a reaction with-in the molten metal.

Lightweight foamed metals having high strength-toweight ratios areextremely useful as load-bearing materials and as heat insulators inelevated temperature systems. Heretofore, these materials have had verylimited usage due in part to their highcost and also to the difficultiesencountered in manufacturing.

In general, extremely close control of processes for producing foamedmetals has been necessary. These methods usually require numerousindividual steps to produce a foam metal. Each step, of course, involvesprecise control techniques. I

One of the problems has been to prevent the escape of the gas used toform the cells within the plastic molten metal mass. the escape of thegas from the molten metal, the degree of foaming is greatly curtailed.

Two of the most common methods used in preventing the degassing of themolten metal are by carrying out the melting under an artificial highpressure system and utilizing alloys wherein there is a wide differencein the alloys solidus and the liquidus temperatures, thus permitting theuse of a melt having a two-phase, liquid plus solid, system. It isgenerally helpful in the latter case that the solid phase predominates.

In the production of foamed metal, that is, metal having a plurality ofrandomly dispersed closed cells throughout a metal matrix, the mostcommon method has been to use a heat decomposable foaming agent togenerate the gas to form the cells. This technique is disclosed in US.Patents 2,751,289 and 2,983,597.

It is, therefore, an object of the present invention to provide a simpleand economical method for producing lightweight foamed metal.

Another object is to provide a simply controlled method of foaming afusible metal.

Still another object is to provide a method of producing a high strength-to-weight ratio metal having a plurality of closed cells randomlydispersed therein.

gYet another object of this invention is to provide a method fordecreasing the fluidity of molten metal during the manufacture of foamedmetal.

A further object is to provide a method of generating a gas within amolten plastic metal mass to foam the plastic melt.

A still further object is to provide a method of retaining gases withina mass of molten metal during the manufacture of foamed metal.

'Yet another object is to provide a method of producing foamed metalwhich is inexpensive, yet adaptable for use in the production of foamedmetals of different metallic compositions.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description whichdiscloses a preferred embodiment thereof.

vThe above objects are accomplished by combining Unless some method isused, to suppress ice particles of a siliceous non-metallic aggregatewith a fusible metal at a temperature above the solidus temperature ofthe metal, but below the metals liquidus temperature. The aggregate iswet by the plastic metal melt and decreases the fluidity of the melt,thus increasing the degree of gas retention by the melt. This decreasedfluidity, i.e. thickening, of the melt enables the foaming operation tobe relatively prolonged and the foamed melt to be maintained in itsheated, fluid condition without collapsingv for a relatively prolongedperiod since the gas bubbles cannot readily escape from thickened melt.

A substance which produces a gas when heated to the temperature of themelt is mixed substantially throughout the molten melt, thereby forminga plurality of gas bubbles'throughout the molten melt and forming amolten foam. Thereafter the foamed melt is cooled below its solidustemperature, thus producing a foamed metal having a plurality of closedcells, formed by the entrapped gaseous bubbles, dispersed within amatrix of the fusible metal.

As a preferred or exemplary embodiment of the instant invention, afusible metal is placed into a suitable receptacle and heated above itssolidus temperature, but below its liquidus temperature, thereby forminga plastic mass of the metal. Among the metals which are preferablyutilized in this process are aluminum, magnesium, zinc, lead, nickel,copper, and alloys of these metals.

The solidus temperature, at which a solid metal is transformed to aliquid or a liquid plus solid phase, varies considerably. For instance,aluminum has a melting point of 1220 F.; magnesium melts at 1202 F.;copper melts at 1981 F.; zinc melts at 787 F.; lead melts at 621 F.; andnickel melts at 2647 F.

For pure metals, the solidus temperature and liquidus temperature arethe same. However, metal alloys will generally have solidus temperatureslower than their liquidus temperature. As used herein, the term plasticconnotates an alloy within the liquid plus solid range.

The plastic range for representative metal alloys are as follows:

Solidus Liquidus Major Metal Constituent Alloy Tempera- Temperature, F.ture, F.

Aluminum 1100 1, 190 1, 215 D 1,190 1, 210 1,160 1, 205 1, 084 1,185 8901, 180 977 1,145 914 1,

When the temperature of an alloy is raised above the solidustemperature, but below the liquidus temperature, it will generallyexhibit a lesser degree of fluidity than when the melt is raised to atemperature where only the liquid phase is present. Even in this range,however, the melt will generally show a substantial degree of fluidity.

With the melt in the plastic range, particles of a siliceousnon-metallic aggregate are mixed throughout the molten metal anddistributed as uniformly as possible throughout the melt. During mixing,the particles are wet by the melt and, as they are dispersedtherethrough, the fluidity of the molten metal is substantiallydecreased. It is necessary that the particles be dispersed substantiallythroughout the melt and remain so in order to insure that the fluidityof the entire melt will be substantially uniform.

It has been found that a number of siliceous materials will decrease thefluidity of molten metals, when used as hereinbefore described. Thesematerials have fusion temperatures above the liquidus temperature ofmetals herein enumerated.

3 Table I lists siliceous non-metallic aggregates, in their hydratedform, that have been used in decreasing the fluidity of a molten alloymelt. Others that may be used include perlite and silica gel.

TABLE I.SILICEOUS MINERALS Mineral: Composition 1 Pyrophyllite Al (Si O(OH) Talc Mg (Si O Mica group:

Muscovite KAl (AlSi O (OI-D Paragonite NaAl (AlSi o (OH) Lepidolite KLiAl(Si O (OI-D Zinnwaldite KLiFeAl(AlSi O (OH) Biotite K(Mg,Fe) (AlSi O(OH) Clintonite group:

Margarite CaAl (Al Si O (OH) (Fe,Mg 2A12 (Alzsizo o) 4- Clintonite Feand Mg partly replace Ca and A1 of margarite.

Illitic minerals Hydrous micas.

Formulas are largely simplified to an ideal type, since most actualcompositions are very complex owing to ISO- morphous substitution.

Although the aggregate particles are preferably added to the melt, theymay be added with the solid metal into the heating container and bebrought up to heat with the metal. Mixing could then be carried out assoon as the metal enters the plastic range.

Once the siliceous non-metallic aggregate particles have been dispersedsubstantially throughout the melt, a gasforming solid, preferably infine particle form, is introduced into the melt and mixed thoroughlytherethrough. During mixing, the melt is preferably maintained at atemperature where the gas-former will be wet by the melt. After mixingis completed, the temperature can be adjusted to that necessary for theformation of gaseous bubbles within the melt.

The generation of bubbles within the melt from the gasformer may becarried out in a number of ways. One of these is the decomposition of aninorganic chemical such as titanium hydride, zirconium hydride, metallicsulfates, and metallic carbonates.

Another technique is the use of a metal or other material which willvaporize at the temperature of the melts, thereby producing the gaseousbubbles within the melt.

Still another method for producing gaseous bubbles within the melt is toadd a material that will react with a component of the melt to producethe gas. This type of reaction would be an oxidation-reduction reactionrather than a decomposition or vaporization reaction.

It has been found that if gas-forming solid particles added to the meltcontain water, the water will be released in the form of steam as theparticles are heated by the melt. It is known that many metals abovehydrogen in the electrochemical series will react with steam to formhydrogen gas and metal oxide, following the general oxidationreductionreaction: M+H O (steam) MOl-H where M represents a metal above hydrogenin the electrochemical series. Depending upon the particular metal, thereaction will take place at different temperatures.

The reactive metal may be present as an alloying element in a melt.Among metallic components within a melt that will react with steam toproduce hydrogen gas are magnesium, iron, titanium, nickel, cobalt, tin,calcium, barium, chromium, manganese, and strontium. It is essentialthat the reactive metal component of the alloy be present at least in anamount that will react with steam to produce H In the case of 1100aluminum more than one of the reactive metals is generally present.Iron, manganese, and magnesium are common constituents of 1100 aluminum,and their effect in the reaction appears. to be additive. Where thereactive metal is magnesium the reaction may occur at a temperature aslow as 700 F., whereas with iron it generally will not take place, atsuitable speeds, below 900 F. The exact temperature may also dependsomewhat on the concentration of the reactive metal.

Once the temperature of the fusible metal alloy is in the plastictemperature range, a water-carrying agent is added to the melt. Thisagent is preferably in small particle form and is rapidly wet by themelt as it is mixed therethrough. As additional quantities of thewater-carrying agent are added, the plastic range of the mixture isincreased.

The amount and size of the water-carrying agent particles to be added tothe melt will, of course, vary, depend ing upon the degree of porosityand density desired in the final product. In general, it is desirablethat the carrying agent contain between one and fifteen percent andpreferably three to nine percent water. In those materials used ascarrying agents which contain relatively large amounts of water, part ofthis water may be driven off by preheating the carrying agent to atemperature sufiicient to liberate some of the water.

Many water-carrying agents have been found useful in this process. Itis, of course, necessary that these materials release their water whenthe particular alloy being used is above its solidus temperature.

Among the materials that may be employed as watercarrying agents aremany siliceous non-metallic aggregates containing water. Examples ofthese aggregates are enumerated hereinbefore, the principal differencebeing that when they are dehydrated they act as thickeners only, but ifthey contain water they may 'be used both as thickeners and as watercarriers.

In addition to these hydrated siliceous aggregates various hydratedinorganic chemicals may be used as watercarrying agents. Among thesechemicals are ammonium ferric sulfate, barium hydroxide, barium iodide,calcium chloride, calcium hydroxide, cerium sulfate, cobalt sulfate,cupric sulfate, ferrous sulfate, lithium sulfite, magnesium sulfate,nickel sulfate, potassium chromium sulfate, potassium sodium tartrate,sodium tetraborate, and zinc sulfate.

The water held by the carrying agent, which is released at the elevatedtemperature to which the agent is subjected, will vary between carryingagent.

In the case of various siliceous non-metallic aggregates, thedehydration temperature will vary between 800 F. and 2250 F. For some ofthese aggregates there is more than one dehydration temperature. Forinstance, talc has three temperature levels where dehydration willoccur. They are at approximately 1652 F., 1697 F. to 1850 F., and 1886F.

As soon as the carrying agent is added to the melt, the mass is stirredvigorously in order to uniformly disperse the carrying agent particlesthroughout the melt. Experimental studies indicate that the method ofmixing carrying agents into the melt is not critical. Any techniquewhich results in relatively uniform distribution of the carrying agentwithin the melt is satisfactory. It is preferable, however, that themixing not subject the carrying agent to extreme shearing which wouldtend to hange the particle size and possibly affect the rate of foaming.

After mixing, the plastic mixture is maintained at a temperature aboveits solidus temperature for a time suflicient for the water held by thecarrying agent to be re-' leased in the form of steam. This time willvary depending upon the temperature at which the fusible metal is heldand also the particular water-carrying agent utilized. Generally suchtime will not be less than 10 seconds nor more than 15 minutes.

As the steam is being released into the melt it chemically reacts withthe reactive component of the fusible metal to form hydrogen gas andreactive metal oxide, according to the general oxidation-reductionreaction 3 as hereinbefore described. Since this reaction will takeplace at different temperatures and rates for different reactive metalsit may sometimes be desirable to raise the melt temperature to bring itinto the liquidus range. This, of course, may not be necessary nordesirable where the oxidation-reduction reaction proceeds at a desiredrate within the plastic temperature range of the melt.

Once the foaming is completed, the melt is allowed to cool below thesolidus temperature of the molten material. As in melting, thistemperature will vary depending upon the fusible metal.

Once cooled below the solidus temperature to the solid state, thelightweight foamed metal may be shaped using conventional tools. If, onthe other hand, a particular configuration is desired, the plastic meltmay be placed into a shaped mold and the melt may be allowed to solidifyin the mold, thus assuming the desired shape. If the melt is placed intothe mold it may be desirable to allow the foaming to occur in the mold.However, this is not necessarily essential. Full or partial foaming maybe allowed to occur prior to placing the melt into the mold.

Upon coo-ling the material below its solidu point, the foamed met-a1will generally have a continuous skin comprised of the fusible metal andrandom particles of the now anhydrous, or substantially so, carryingagent. The interior of the foamed composition of matter will contain aminor volume of random, substantially uniformly dispersed particles ofanhydrous carrying agent and a plurality of discrete closed cells, somepossibly being interconnected, substantially randomly dispersed withinthe solid fusible metal matrix.

As used in this specification, the term closed cell means a singlepocket formation or a plurality of interconnected pockets sealed withinthe solid metal. It is not to be construed to mean an open cellstructure, as is found in a sponge.

Various other methods, such as the decomposition and vaporizationtechniques hereinbefore mentioned, may be utilized to generate the gaswithin the melt for producing the foam.

On the other hand, foaming, using the oxidation-reduction method forproducing the gas, may be carried out without the necessity ofdecreasing the fluidity of the melt, if precise controls are employed inmaintaining the melt at the proper plastic temperature range duringfoaming and then solidifying the foamed melt rapidly before the gaseousbubbles escape.

An alternate technique may be used in adding the watercarrying agent tothe metal alloy.v In this form of the invention small particles of boththe fusible metal and the non-metallic water-carrying agent arethoroughly comnringled and then heated in a furnace above the solidustemperature. The plastic melt is then thoroughly blended.

While the water-carrying agent is substantially uniformly distributedthroughout the melt, the water is released into the melt in the form ofsteam, and the oxidationreduction reaction with the reactive componentof the alloy, as described hereinbefore, takes place.

The following examples are by way of explanation and are not to beconsidered limitations on the invention.

Example 1 100 grams of 5052 aluminum alloy were placed in a crucible andheated to a temperature of 1130 F. thereby transforming the aluminum tothe liquid plus solid state. Into the molten aluminum was introduced 3grams of 100-mesh expanded dehydrated vermiculite. The mixture ofaluminum and vermiculite was then mixed thoroughly for a period of 3minutes. As soon as the vermiculite was dispersed substantiallythroughout the molten aluminum, 1 gram of No. 4 expanded vermiculite (amixture of 16- 50 mesh) containing 5 percent water was added to themixture while the melt was heated to 1300 F., during which time thewater contained within the second vermiculite addition was released assteam and reacted with magnesium within the alloy to form a plurality ofbubbles within the melt. The melt was then cooled below its solidustemperature, thereby forming a solid foamed metal.

Example 2 100 grams of 4043 aluminum alloy were placed in a furnace andheated to 1130 F thereby transforming the aluminum to the plastic state.Into this molten aluminum was introduced 4 grams of 100-mesh expandeddehydrated vermiculite which was thoroughly mixed and dispersedthroughout the aluminum thereby thickening the melt. Into the mixturewas added 10 grams of a powdered mixture consisting of 1.5 grams of ZrHin 8.5 grams of an eutectic mixture of aluminum and magnesium. Thispowder was dispersed throughout the molten melt. Upon reachingapproximately 1160" F. each of the ZrH; particles decomposed andreleased a quantity of hydrogen gas bubbles. Thereupon the melt wascooled below its solidification temperature producing a foamed metalhaving a plurality of dispersed closed cells, substantially filled withhydrogen therein, and particles of vermiculite dispersed throughout thematrix of aluminum alloy.

Exam ple 4 grams of an alloy composed of 3.5% magnesium and 96.5% ofcommercially pure aluminum, having a density of approximately 2.67 gramsper cubic centimeter, was melted and maintained in the solid plus liquidplastic range while 7 grams of No. 4 grade expanded vermiculite,containing 4.8% water was mixed into the melt. The addition and mixingof the vermiculite into the molten aluminum alloy took place over aperiod of 4 minutes. After mixing, the melt was allowed to remain in thefurnace for an additional 3 minutes at 1300 F. and then cooled below thesolidus temperature. The resulting lightweight foamed alloy had adensity of approximately 1.05 grams per cubic centimeter.

Example 5 20 grams of 5086 aluminum alloy having a density of 2.65 gramsper cubic centimeter were cut into small crescent-shaped particlesweighing about 0.08 gram each. These particles were then mixed with 0.65gram of No. 4 grade vermiculite containing about 5% water. Thealuminum-vermiculite mixture was then placed in a furnace which had beenpreheated to about 1180 F. and vigorously mixed as the temperature ofthe mixture rose above 1084 F. After the now plastic mixture had 'beenstirred sufficiently to insure even distribution of the vermiculitethroughout the melt, the mixture was allowed to remain in the furnacefor an additional 3 minutes. It was then removed from the furnace forrapid air cooling below the solidus temperature. The foamed aluminumstructure resulting had a density of approximately 1.3 grams per cubiccentimeter.

Example 6 15 grams of magnesium particles were introduced into 60 gramsof molten'zinc. The temperature of the melt was adjusted toapproximately 1040" F. and 8 ml. of 40-60 mesh vermiculite wereintroduced. The plastic mixture was then stirred sufficiently to insureeven distribution of the vermiculite throughout the melt and allowed tofoam for approximately 10 minutes. The foamed melt was then cooled belowits solidus temperature there-by forming a solid Zn-Mg foamed alloy.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description, and it will beapparent that various changes may be made in the steps of the methoddescribed and the order of accomplishment without departing from thespirit and scope of the invention or sacrificing all of its materialadvantages, the form hereinbefore described being merely a preferredembodiment thereof.

We claim: 1. A method of producing foamed metal wherein gaseous bubblesare retained within a mass of molten metal during the foaming,comprising the steps of:

heating a fusible metal and particles of a siliceous nonmetallicaggregate above the solidus temperature of said metal, but below theliquidus temperature of said metal, whereby said solid aggregatedispersed within the molten metal decreases the normal fluidity of saidmolten metal; introducing a substance which produces a gas when heatedto the temperature of the melt into said me'lt;

mixing said substances substantially throughout the melt, therebyproducing a plurality of gas bubbles throughout said melt and forming afoamed melt, said gas being retained within said melt due principally tothe high viscosity of said melt resulting from said dispersed aggregateparticles; and

cooling said foamed melt below the solidus temperature of said melt toform a foamed metal having a plurality of close-d cells and particles ofsaid nonmetallic aggregate disperse-d within a matrix of said fusiblemetal; 2. The method of claim 1 wherein said siliceous nonmetallicaggregate particles are selected from the group consisting ofvermiculite, perlite, talc, silica gel, pyrophyllite, mica andclintonite.

3-. The method of claim 2 wherein said siliceous nonmetallic aggregateparticles are substantially anhydrous. 4. The method of claim 2 whereinsaid particles of siliceous non-metallic aggregate comprise less than50% of said melt.

5. The method of claim 1 wherein said fusible metal is selected from thegroup consisting of aluminum, magnesium, zinc, lead, copper, nickel, andalloys of said metals.

6. The method of claim 5 wherein said fusible metal is an aluminumalloy.

7. The method of claim 5 wherein said fusible metal is a magnesiumalloy.

8. The method of claim 1 wherein said molten metal wets saidnon-metallic aggregate.

9. A method of manufacturing a substantially rigid lightweight foamedmetal alloy, comprising the steps of: heating a fusible metal having asolidus temperature between 700 F. and 2000 F. to a temperature abovethe solidus temperature of said metal, thereby forming a plastic melt ofsaid fusible metal, said metal containing at least one metallic alloyingelement that reacts with steam to form hydrogen;

introducing non-metallic water-carrying agent particles into said melt;

mixing said carrying agent particles into said melt between the solidusand liquidus temperatures of said melt to disperse said particlessubstantially uniformly throughout said melt;

maintaining the molten mixture at a temperature above the solidustemperature of said mixture until the water held by said carrying agentparticles is released in the form of steam, said steam then reactingwith said metal alloying element to produce a plurality of hydrogenbubbles throughout said melt, thereby forming a foamed molten melt; and

.cooling the melt below its solidus temperature and entrapping said ydog n 'bl bbies within a matrix 8 of said fusible metal thereby forming asolid lightweight foamed metal comprising a solid fusible metal matrix,particles of an anhydrous carrying agent dispersed within said matrix,and a plurality of discrete closed cells Within the solid fusible metal.10. The method of claim 9 wherein said molten mixture is maintainedbetween its solidus temperature and liquidus temperature during therelease of said water from said carrying agent particles.

11. The method of claim 9 wherein said metal alloying element isselected from the group consisting of magnesium, iron, titanium, nickel,cobalt, tin, calcium, chromium, barium, manganese and strontium.

12. The method of claim 9 wherein said molten melt wets saidwater-carrying agent.

13. The method of claim 9 wherein said water-carrying agent particlesare selected from the group consisting of vermiculite, perlite, talc,silica gel, pyrophyllite, mica and clintonite.

14. A method of manufacturing a substantially rigid lightweight foamedmetal, comprising the steps of:

mixing particles of a fusible metal having a solidus temperature between700 F. and 2000 F. with particles of a non-metallic water-carryingagent, said metal containing at least one metal-lie alloying elementthat reacts with steam to form hydrogen;

heating said mixture to a temperature above the solidus temperature ofsaid fusible metal but below the fusion point of said water-carryingagent, thereby forming a plastic mass;

mixing said plastic mass between the solidus and liquidus temperaturesof said mass until said carrying agent particles are dispersedsubstantially uniformly throughout said melt;

maintaining the molten mixture at a temperature above the solidustemperature of said mixture until the water held by said carrying agentparticles is released in the form of steam, said steam then reactingwith said metal alloy element to produce a plurality of hydrogen bubblesthroughout said melt, thereby forming a foamed molten melt; and

cooling the melt below its solidus temperature and entrapping saidhydrogen bubbles in the matrix of fusible metal, thereby forming alightweight foamed metal comprising a solid fusible metal matrix,particles of an anhydrous carrying agent dispersed within said matrix,and a plurality of discrete closed celis within the solid fusible metal.

15. The method of claim 14 wherein said metallic alloying element isselected from the group consisting of magnesium, iron, titanium, nickel,cobalt, tin, calcium, chromium, manganese and strontium.

16. The method of claim 15 wherein the fusible metal melt wets saidparticles of non-metallic water-carrying agent.

17. The method of claim 15 wherein said water-carrying agent particlesare selected from the group consisting of vermiculite, perlite, talc,silica gel, pyrophyllite, mica and clintonite.

18. In a method of producing a closed cell foamed metal whereby agas-producing substance different from said metal is utilized to producea plurality of randomly dispersed closed cells within a molten melt ofsaid metal and said melt is then cooled below its solidus temperature toform a solid foamed metal comprising a solid metal matrix and aplurality of closed cells dispersed substantially the-rethroughout, thestep of:

Wetting dispersed particles of a solid non-metallic siliceous aggregatewithin said melt of said fusible metal at a temperature above thesolidus temperature of said metal, but below the liquidus temperature ofsaid metal and below the fusion temperature of said aggregate, wherebysaid dispersed solid aggregate decreases the normal fiuidity'of saidmolten metal, thereby increasing the gaseous retention properties ofsaid melt for a period of time during subsequent foaming.

19. The method of claim 18 wherein said siliceous nonmetallic aggregateparticles are selected from the group consisting of vermiculite,perlite, talc, pyrophyllite, silica gel, mica and clintonite.

20. The method of claim 19 wherein said siliceous nonmetallic aggregateparticles are substantially anhydrous.

21. The method of claim 18 wherein said particles of siliceousnon-metallic aggregate comprise less than 50% of said melt by volume.

22. In a method of manufacturing a substantially rigid lightweightfoamed metal wherein a molten melt of fusible metal at a temperatureabove the solidus temperature of said metal is foamed by the dispersionof gaseous bubbles therethrough and the melt is then cooled below itssolidus temperature whereby said gaseous bubbles are entrapped within amatrix of fusible metal, thereby forming a solid lightweight foamedmetal comprising a solid fusible metal matrix and a plurality ofdiscrete closed cells dispersed within said matrix, the stepscomprising:

adding particles of a gas-producing substance which chemically reactswith at least one component of said molten melt in anoxidation-reduction reaction to form a gas;

mixing said particles into said melt between the solidus and liquidustemperatures of said melt to wet and disperse said particlessubstantially uniformly throughout said melt; and

maintaining the molten mixture above the solidus temperature of saidmixture while a chemical oxidationreduction reaction occurs between saidparticles and said component of said melt to produce said gaseousbubbles, thereby foaming said melt.

23. The method of claim 22 wherein said oxidationreduction reactionproduces hydrogen gas bubbles.

24. The method of claim 23 wherein said hydrogen gas bubbles areproduced by an oxidation-reduction reaction between steam and saidcomponent.

25. The method of claim 24 wherein said component is a metallic elementselected from the group consisting of magnesium, iron, titanium, nickel,cobalt, tin, calcium, barium, chromium, manganese and strontium.

26. The method of claim 24 wherein said gas-producing substance is awater-carrying non-metallic inorganic chemical.

27. A metal foam body, comprising:

a metal matrix having dispersed therethrough a plurality of completelyclosed cells substantially filled with gas;

and solid non-metallic siliceous particles dispersed within said matrixwherein said solid non-metallic siliceous particles comprise less thanweight percent of said foam body.

28. The foam body of claim 27 wherein said gas is hydrogen.

29. The foam body of claim 27 wherein said siliceous particles areselected from the group consisting of vermiculite, perlite, talc, silicagel, pyrophyllite, mica and clintonite.

References Cited by the Examiner UNITED STATES PATENTS 2,895,819 7/1959Fiedler --20 2,935,396 5/1960 Pashak 75-20 2,983,597 5/1961 Elliott 75203,055,763 9/1962 Kreigh et al.

BENJAMIN HENKIN, Primary Examiner,

1. A METHOD OF PRODUCING FOAMED METAL WHEREIN GASEOUS BUBBLES ARERETAINED WITHIN A MASS OF MOLTEN METAL DURING THE FOAMING, COMPRISINGTHE STEPS OF: HEATING A FUSIBLE METAL AND PARTICLES OF A SILICEOUSNONMETALLIC AGGREGATE ABOVE THE SOLIDUS TEMPERATURE OF SAID METAL, BUTBELOW THE LIQUIDUS TEMPERATURE OF SAID METAL, WHEREBY SAID SOLIDAGGREGATE DISPERSED WITHIN THE MOLTEN METAL DECREASES THE NORMALFLUIDITY OF SAID MOLTEN METAL; INTRODUCING A SUBSTANCE WHICH PRODUCES AGAS WHEN HEATED TO THE TEMPERTURE OF THE MELT INTO SAID MELT; MIXINGSAID SUBSTANCES SUBSTANTIALLY THROUGHOUT THE MELT, THEREBY PRODUCING APLURALITY OF GAS BUBBLES THROUGHOUT SAID MELT AND FORMING A FOAMED MELT,SAID GAS BEING RETAINED WITHIN SAID MELT DUE PRINCIPALLY TO THE HIGHVISCOSITY OF SAID MELT RESULTING FROM SAID DISPERSED AGGREGATEPARTICLES; AND COOLING SAID FOAMED MELT BELOW THE SOLIDUS TEMPERATURE OFSAID MELT TO FORM A FOAMED METAL HAVING A PLURALITY OF CLOSED CELLS ANDPARTICLES OF SAID NONMETALLIC AGGREGATE DISPERSED WITHIN A MATRIX OFSAID FUSIBLE METAL.
 27. A METAL FOAM BODY, COMPRISING: A METAL MATRIXHAVING DISPERSED THERETHROUGH A PLURALITY OF COMPLETELY CLOSED CELLSSUBSTANTIALLY FILLED WITH GAS; AND SOLID NON-METALLIC SILICEOUSPARTICLES DISPERSED WITHIN SAID MATRIX WHEREIN SAID SOLID NON-METALLICSILICEOUS PARTICLES COMPRISE LESS THAN 50 WEIGHT PERCENT OF SAID FORMBODY.